There is at present no valid radioisotopic leukocyte label for scanning studies. The overall objective of this project is to develop methodology by which whole-body scanning of the distribution patterns of technetium-99 labeled autologous peripheral blood lymphocytes and granulocytes can become an established clinical procedure. We have employed 99mTc as a label for studying lymphocyte distribution patterns in both mice and rabbits and have investigated 99mTc-granulocyte distribution in rabbits and in normal adult human volunteers. These studies have clearly demonstrated the feasibility of using 99mTc as a radioisotopic label to image leukocyte distribution. The objectives of the present project are fivefold: 1. To develop improved methodology for the direct labeling of human peripheral blood lymphocytes and granulocytes with 99mTc. Phagocytic and direct labeling procedures for granulocytes will be compared with direct labeling by 99mTc. 2. To study the distribution patterns of 99mTc labeled lymphocytes and granulocytes in normal adult volunteers. Blood clearance will be determined by gamma scintillation counting and organ distribution by whole body scanning. 3. To determine whether 99mTc labeled granulocytes can be used to detect occult pyogenic abscesses. 4. To evaluate 99mTc leukocyte scanning for the diagnosis of early renal allograft rejection from cadaveric donors. The localization of 99mTc labeled cells at the site of the allograft may be an early warning of rejection which otherwise might not be detected until a fully developed rejection crisis had developed. 5. To study the distribution patterns of 99mTc labeled lymphocytes and granulocytes in patients with leukemia and lymphoma. Distribution patterns will be related to the clinical course. The relationship between T and B cell markers, cell surface charge, and organ distribution patterns will be investigated. These studies should establish the clinical usefulness of 99mTc as a leukocyte label for gamma tracer and imaging studies in man.